1. Field of the Invention
The present invention relates to a brake and steering knuckle assembly for a steer axle on a medium or heavy duty truck. More specifically, the present invention relates to a brake and steering knuckle assembly for the steer axle on a medium or heavy duty truck where the steering knuckle provides for the direct support of the brake shoes and brake activation device without a brake spider.
2. Description of the Prior Art
It is well known in the prior art to use an "S-cam" to actuate a pair of arcuate brake shoes to contact the inner surface of a brake drum to provide a frictional braking force to a vehicle wheel assembly. Although the present invention is not strictly limited to rotary cam brakes of the S-cam type, but could be used with various other configurations of rotary cam brakes, the invention is especially advantageous when used with S-cam expanding internal shoe drum brakes, and will be described in connection therewith. An example of a typical S-cam expanding internal shoe drum brake is disclosed in U.S. Pat. No. 4,905,800 assigned to the assignee of the present invention and incorporated herein by reference. Traditionally, the brake shoes and the rest of the braking components making up the brake assembly are mounted to what is known in the art as a "brake spider" which is attached to the steer knuckle and supports the brake shoes and the S-cam actuation device.
It is desirable to minimize the overall package of the brake assembly to facilitate placement within the confines of the vehicle wheel while providing for the required braking performance in extreme conditions. It is also desirable to minimize the number of components required to provide for the braking function thereby minimizing complexity, weight and expense. Thus, elimination of the brake spider is desirable for many practical reasons.
Attachment of the tie-rod arm and the steering arm in a traditional steering knuckle assembly by threaded fasteners results in packaging problems with the brake camshaft assembly, a relatively high weight-to-strength ratio, and a significant increase in steering system deflection. The relative motion that can occur with or without input from the driver resulting in undesired steering inputs into the wheel assembly. There is commonly available a steering knuckle for heavy duty motor vehicles such as trucks, wherein the steering arm and the tie-rod are fitted to the steering knuckle by means of a threaded portion in a fastening nut. There is a need in the heavy duty motor vehicle field to provide a steering knuckle assembly wherein the tie-rod arm and the steering arm are integrally formed as a one piece unit with the steering knuckle. This configuration would result in higher strength-to-weight ratio, improved brake assembly packaging and more accurate steering of the vehicle by improving the integrity of the connection between the tie-rod arm, the steering arm, and the knuckle. An example of such a steering knuckle is described in U.S. Pat. No. 5,219,176 the disclosure of which is hereby incorporated by reference. These heavy duty steering knuckles also employ flange body to which a separately attached brake spider unit for connection to the brake assembly as previously discussed.